WO2015114805A1

WO2015114805A1 - Method and device for treating heavy-metal-containing wastewater

Info

Publication number: WO2015114805A1
Application number: PCT/JP2014/052289
Authority: WO
Inventors: 河原林　直也; 渡辺　実
Original assignee: 栗田工業株式会社
Priority date: 2014-01-31
Filing date: 2014-01-31
Publication date: 2015-08-06

Abstract

The purpose of the present invention is to enable a dithiocarbamic-acid-based heavy-metal scavenger to be introduced into a heavy-metal-containing wastewater in a proper amount, which is neither too large nor too less, when the wastewater is treated with the scavenger. In the method and device for treating a heavy-metal-containing wastewater, an inorganic coagulant is added to the heavy-metal-containing wastewater to cause coagulation, a dithiocarbamic-acid-based heavy-metal scavenger is then added thereto, and thereafter solid-liquid separation is conducted. A heavy-metal compound is added to the heavy-metal-containing wastewater to which the dithiocarbamic-acid-based heavy-metal scavenger has been added, and the heavy-metal compound is reacted with the dithiocarbamic-acid-based heavy-metal scavenger contained in the water to develop a color. Thereafter, the absorbance or transmittance at a wavelength of 400-700 nm is measured. Based on the results of the measurement, the amount of the dithiocarbamic-acid-based heavy-metal scavenger to be added is controlled.

Description

Method and apparatus for treating wastewater containing heavy metals

The present invention relates to a treatment method and apparatus for heavy metal-containing wastewater, and in particular, after adding an inorganic flocculant to heavy metal-containing wastewater, a dithiocarbamic acid-based heavy metal collector is added to remove heavy metal components in the wastewater. The present invention relates to a processing method and apparatus.

重 Heavy metal-containing wastewater such as plating wastewater and paint wastewater contains heavy metals such as copper, chromium, zinc, lead, manganese, iron, nickel, and cadmium. These heavy metal-containing wastewater is obliged to be treated appropriately by the Water Pollution Control Law.

As a method for treating heavy metal-containing wastewater, a method is known in which a chelating heavy metal scavenger mainly composed of dithiocarbamic acid groups is added to perform a coagulation sedimentation treatment (Patent Document 1). In the treatment method of heavy metal containing wastewater using this dithiocarbamic acid type heavy metal scavenger, chelate heavy metal scavenger addition is performed when chelating heavy metal scavenger is added and treated regardless of the water quality fluctuation of heavy metal containing wastewater. When the amount is insufficient, the quality of the treated water is lowered due to heavy metal leakage, and when it is excessively added, the quality of the treated water is lowered by the chelating heavy metal scavenger itself.

In Patent Document 1, as a method of adding a chelate heavy metal scavenger to heavy metal-containing wastewater to remove heavy metal components in the wastewater, a chelate heavy metal scavenger is added to the heavy metal-containing wastewater, Measure the addition amount of the collector and the amount of change in the oxidation-reduction potential of the wastewater before and after the addition of the chelate heavy metal scavenger, and determine the required addition amount of the chelate heavy metal scavenger based on this measurement result A method is described.

The chelate heavy metal scavenger has a chelate-forming group (dithiocarbamic acid group), and this group reacts with heavy metal ions in the wastewater to form an insolubilized product and generate a precipitate. During this reaction, the redox potential (ORP) decreases. According to the method of Patent Document 1, when the ORP is changed, that is, when the addition concentration of the chelate heavy metal scavenger to the wastewater to be treated is changed, the ORP becomes lower as the addition concentration of the heavy metal scavenger increases. It is used to change.

Patent Document 2 describes the following method. A sample is taken from a waste such as a heavy metal extraction treatment product, a liquid chelating agent is added to a predetermined amount of the sample, the heavy metal in the sample is reacted with the liquid chelating agent, and the sample to which the liquid chelating agent is added, The absorbance IB at a specific wavelength for the liquid chelator is determined. The amount B of the unreacted liquid chelating agent in the sample is obtained from the absorbance IB, the absorbance IA at a wavelength corresponding to the total amount of the liquid chelating agent added by the blank test is obtained, and the total amount A of the liquid chelating agent added from the absorbance IA is obtained. Ask. From the difference between the total amount A and the amount B, the amount C of the liquid chelating agent that has reacted with the heavy metal is determined. Based on the ratio between the amount C and the predetermined amount of sample, the appropriate amount of liquid chelating agent added to treat the waste is determined. Patent Document 2 describes 286 nm, 257 nm, and 215 nm as wavelengths used for measuring absorbance when the chelating agent is a dithiocarbamic acid type.

Patent Document 3 describes a method of insolubilizing heavy metal-containing fly ash with a dithiocarbamic acid chelating agent. Patent Document 3 describes that the concentration of a chelating agent in a liquid is measured by absorbance at a wavelength of 330 nm or more (specifically, 350 nm) (paragraphs 0018 and 0028 of patent document 3).

Since the determination of the dithiocarbamic acid chelating agent by the absorbance method in

Patent Documents

2 and 3 detects the absorbance of the dithiocarbamic acid chelating agent itself, the concentration of the dithiocarbamic acid chelating agent such as treatment of waste water containing heavy metals When it is low, or when the concentration of organic substances in the test water that affects the absorbance varies, the measurement accuracy is low.

In order to solve this problem, the applicant of the present application first added a dithiocarbamate heavy metal collector to a heavy metal-containing wastewater to remove the heavy metal component in the wastewater. As a method for determining the required addition amount, a dithiocarbamic acid heavy metal scavenger is added to the wastewater containing heavy metal, and after adding this dithiocarbamic acid heavy metal scavenger, a heavy metal compound is added to the solid-liquid separated treated water, and heavy metal ions are added. After reacting with the dithiocarbamate heavy metal collector in the treated water to develop color, the absorbance or transmittance at a wavelength of 400 to 700 nm is measured, and the dithiocarbamate heavy metal collector is measured based on the measurement result. Has proposed a method of controlling the amount of addition (Patent Document 4).
In Patent Document 4, specifically, a dithiocarbamic acid heavy metal scavenger is added to the heavy metal-containing wastewater, the heavy metal in the wastewater is reacted with the scavenger to insolubilize, and then an inorganic flocculant is added to the reaction liquid Then, the polymer flocculant is added, and then a polymer flocculant is added to further agglomerate, followed by solid-liquid separation, and a heavy metal compound is added to the treated water subjected to solid-liquid separation.

JP 2001-340874 A JP-A-10-337550 JP 2010-260010 A JP2012-161724

According to the method of Patent Document 4, color is developed by the reaction of a heavy metal ion and a dithiocarbamic acid heavy metal collector, and the absorbance or transmittance in the visible light region of 400 to 700 nm is measured. Residual scavengers can be accurately detected or quantified even when the concentration of organic substances that affect the absorbance or transmittance fluctuates without being affected by absorption, but dithiocarbamic acid-based wastewater containing heavy metals Since the inorganic flocculant is added after adding the heavy metal collector, the residual dithiocarbamic acid heavy metal collector that did not react with the heavy metal ions reacts with the inorganic flocculant, and the measurement accuracy of the residual collector There was a problem of low.

The present invention provides a method and apparatus for treating heavy metal-containing wastewater with an inorganic flocculant and a dithiocarbamic acid-based heavy metal scavenger, thereby measuring the residual scavenger with high accuracy, thereby increasing the amount of heavy metal scavenger injection. An object of the present invention is to provide a heavy metal-containing wastewater treatment method and apparatus capable of obtaining treated water with an appropriate amount without deficiency and having good water quality.

The method for treating heavy metal-containing wastewater according to the present invention is a method for treating heavy metal-containing wastewater, which is obtained by adding an inorganic flocculant to the heavy metal-containing wastewater and then aggregating, then adding a dithiocarbamic acid heavy metal scavenger, and then solid-liquid separation. About. In the present invention, a heavy metal compound is added to the heavy metal-containing wastewater to which the dithiocarbamic acid heavy metal scavenger is added, if necessary, and the heavy metal compound reacts with the dithiocarbamic acid heavy metal scavenger in the water to cause color development. Next, the absorbance or transmittance at a wavelength of 400 to 700 nm is measured, and the addition amount of the dithiocarbamic acid heavy metal scavenger is controlled based on the measurement result.

The apparatus for treating heavy metal-containing wastewater according to the present invention comprises a means for adding an inorganic flocculant to a heavy metal-containing wastewater for agglomeration, a means for adding a dithiocarbamic acid heavy metal scavenger, and then a solid-liquid separation for solid-liquid separation. Separating means. The apparatus of the present invention includes means for adding a heavy metal compound to a heavy metal-containing wastewater to which a dithiocarbamic acid heavy metal scavenger is added, as necessary.

The apparatus of the present invention further comprises means for measuring the absorbance or transmittance at a wavelength of 400 to 700 nm after reacting the heavy metal compound with the dithiocarbamic acid heavy metal scavenger in the water to cause color development, And a control means for controlling the amount of the dithiocarbamic acid heavy metal scavenger added.

The water-soluble iron salt or copper salt is suitable as the heavy metal compound for color development.

It is preferable to control the addition amount of the heavy metal scavenger so that the concentration of the dithiocarbamic acid heavy metal scavenger in water determined from the absorbance or transmittance is 2 to 30 mg / L.

In the method and apparatus for controlling the chemical injection of heavy metal collector of the present invention, when determining the amount of dithiocarbamic acid heavy metal collector to be added to wastewater containing heavy metal, the inorganic flocculant and dithiocarbamic acid heavy metal collector are added to the wastewater. Agents are added in this order, and solid-liquid separation is performed. If necessary, heavy metal compounds such as water-soluble iron salts and copper salts can be added to waste water containing heavy metals containing dithiocarbamic acid heavy metal collectors (hereinafter sometimes referred to as “heavy metal collector-added water”). After adding and reacting heavy metal ions with the residual dithiocarbamic acid heavy metal scavenger to develop color, the absorbance or transmittance at 400 to 700 nm is measured. In this way, color is developed by the reaction between the heavy metal ion and the dithiocarbamic acid heavy metal collector, and the absorbance or transmittance in the visible light region of 400 to 700 nm is measured, so that it is affected by the visible light absorption of the collector. Even if the organic substance concentration that affects the absorbance or transmittance varies, the residual collection agent can be detected or quantified with high accuracy. An absorbance sensor or transmittance sensor of 400 to 700 nm is less expensive than a UV absorbance sensor or the like.

In the present invention, since the dithiocarbamic acid heavy metal scavenger is added after the inorganic flocculant is added to the heavy metal-containing wastewater, the dithiocarbamic acid heavy metal scavenger is prevented or suppressed from reacting with the inorganic flocculant. Thus, the residual dithiocarbamic acid heavy metal scavenger that has not reacted with the heavy metal ions in the wastewater can be measured with high accuracy. When the inorganic flocculant is added after adding the dithiocarbamic acid heavy metal collector to the heavy metal-containing wastewater as in Patent Document 4, the residual dithiocarbamic acid heavy metal collector that did not react with the heavy metal ions reacts with the inorganic flocculant. Thus, the measurement accuracy of the residual collection agent is lowered, but the present invention solves such a problem.

In the present invention, since the inorganic flocculant is used in combination, the quality of the solid-liquid separation treated water is good. Since the inorganic flocculant is added prior to the addition of the dithiocarbamic acid-based heavy metal scavenger, the suspended matter and part of the soluble COD in the heavy metal-containing wastewater are coagulated. Thereby, the measurement accuracy of absorbance or transmittance is further improved.

It is a flowchart which shows the chemical injection control method and apparatus of the heavy metal scavenger which concerns on embodiment. It is a flowchart which shows the chemical injection control method and apparatus of the heavy metal scavenger which concerns on another embodiment. It is a graph which shows the light absorbency of a heavy metal scavenger. It is a graph which shows the light absorbency when Fe ^<2+> is added to the dithiocarbamic-acid type heavy metal collection agent aqueous solution. It is a graph which shows the light absorbency when Fe ^<2+> is added to the dithiocarbamic-acid type heavy metal collection agent aqueous solution. It is a graph which shows a light absorbency when the dithiocarbamic acid type heavy metal scavenger aqueous solution is added to Fe ^<2+ >. It is a graph which shows a light absorbency when Cu ^<2+> is added to the dithiocarbamic-acid type heavy metal collection agent aqueous solution. It is a graph which shows a light absorbency when Fe ^<3+> , Al ^<3+> or Ca ^<2+> is added to the dithiocarbamic-acid type heavy metal scavenger aqueous solution. It is a graph which shows a light absorbency when Cu ^<2+> or Fe ^<2+> is added to the dithiocarbamic-acid type heavy metal collection agent aqueous solution. It is a graph which shows a light absorbency when Cu ^<2+> is added to the dithiocarbamic-acid type heavy metal collection agent aqueous solution.

Hereinafter, the present invention will be described in more detail.

In the present invention, an inorganic flocculant and a dithiocarbamic acid heavy metal scavenger are added to the heavy metal-containing wastewater in this order, and the heavy metal in the wastewater is reacted with the scavenger to insolubilize, and then solid-liquid separation is performed. .

This heavy metal-containing wastewater includes steel, semiconductor, and automobile manufacturing plating processes, smoke cleaning of garbage factories and power plants, dust collection processes, batteries, glass manufacturing processes, metal processing processes, landfill leachate from industrial waste treatment plants, etc. Although the drainage from is illustrated, it is not limited to this.

Examples of heavy metals in the heavy metal-containing wastewater include, but are not limited to, mercury, cadmium, arsenic, lead, hexavalent chromium, selenium, copper, zinc, manganese, divalent iron, nickel, and trivalent iron. .

The heavy metal ion concentration in the wastewater containing heavy metal is usually about 100 ppm or less, for example, about 1 to 50 ppm, but is not limited thereto.

In the present invention, an inorganic flocculant is first added to the heavy metal-containing wastewater to be agglomerated.

Examples of the inorganic flocculant include iron-based inorganic flocculants such as polyferric sulfate and ferric chloride, and aluminum-based inorganic flocculants such as polyaluminum chloride and aluminum sulfate, but are not limited thereto.

By this agglomeration treatment of the inorganic flocculant, at least a part of suspended substances and soluble COD in heavy metal-containing wastewater is agglomerated, improving the quality of the treated water and improving the accuracy of the subsequent absorbance or transmittance measurement. To do.

The amount of inorganic flocculant added is usually about 10 to 1000 mg / L, although it varies depending on the content of suspended substances and soluble COD in the heavy metal-containing wastewater. After the addition of the inorganic flocculant, it is preferable to perform an agglomeration treatment for about 5 to 30 minutes.

It is preferable to adjust the pH by adding an acid or alkali after the addition of the inorganic flocculant to insolubilize the metal ions in the inorganic flocculant.

After adding an inorganic flocculant and, if necessary, acid or alkali, and preferably performing agglomeration by stirring, a dithiocarbamic acid heavy metal scavenger is added to the agglomeration liquid, preferably without solid-liquid separation. .

Dithiocarbamate heavy metal scavengers include dithiocarbamate, dialkyldithiocarbamate, cycloalkyldithiocarbamate, piperazine bisdithiocarbamate, tetraethylenepentamine dithiocarbamate, polyethyleneimine benzyl chloride condensate carbon disulfide, Examples include, but are not limited to, sodium hydroxide modified products, polyamine dithiocarbamate, and the like. In addition, these 1 type may be used independently and may use 2 or more types together.

An insolubilized product is generated by adding a dithiocarbamic acid heavy metal scavenger to the heavy metal-containing wastewater and preferably stirring slowly. The reaction time with the dithiocarbamic acid heavy metal scavenger is preferably about 5 to 60 min. The pH during the insolubilization product formation reaction is usually 6 to 11, and an acid or alkali is added as necessary to adjust the pH.

It is preferable to add a polymer flocculant to this insolubilized material-containing liquid, and preferably agitate slowly to agglomerate the inorganic flocculant and this insolubilized material. By adding the polymer flocculant, it is possible to further improve the quality of the treated water.

Polymer flocculants include anionic polymer flocculant homopolymers of acrylamide, copolymers of sodium acrylate and acrylamide, terpolymers of sodium acrylate, acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. Can be used. The amount of the polymer flocculant added varies depending on the amount of the aggregate and insolubilized product produced depending on the quality of the wastewater containing heavy metal, but is usually 0.5 to 5 mg / L. It is preferable to carry out for about 10 minutes.

The liquid containing the insolubilized material generated by adding the dithiocarbamic acid heavy metal scavenger is subjected to a solid-liquid separation process after adding a polymer flocculant and aggregating as necessary. The solid-liquid separation means may be any of sedimentation separation, filtration, centrifugation, membrane separation, and the like.

As heavy metal compounds that are added as necessary to the heavy metal scavenger addition water and react with the residual scavenger to develop color, Fe ²⁺ , Fe ³⁺ , Cu ²⁺ , Zn ²⁺ , Pb ²⁺ , Ni ²⁺ , Cd ²⁺ , Examples include sulfate salts such as Mn ^2+, and water-soluble salts such as hydrochloride salts. However, since no special treatment is required at the time of discharge after the degree of color development or analysis, a salt of Fe ²⁺ or Fe ³⁺ , for example, first chloride Iron, ferrous sulfate, ferric chloride, and ferric sulfate are preferred.

The heavy metal compound can be added to any liquid as long as it is water after a dithiocarbamic acid heavy metal scavenger is added and an insolubilized product is formed. It can be added to the treated liquid or treated water after the solid-liquid separation treatment.

In general, when the heavy metal compound is added to a dilute aqueous solution of the dithiocarbamic acid heavy metal scavenger, the color becomes deeper as the amount of the heavy metal compound increases, but the total amount of the scavenger in water and the added heavy metal compound When the reaction equivalent is exceeded, the color development does not become deeper even if the amount of heavy metal compound added is increased. Therefore, in the present invention, when the residual scavenger concentration in the heavy metal scavenger-added water is quantified, the heavy metal compound is more than the above reaction equivalent (for example, about 1 to 10 times, particularly about 1.5 to 5 times the reaction equivalent). Is preferably added. Usually, it is desirable to add a heavy metal compound as heavy metal ions in an amount of 10 mg / L or more, particularly 20 mg / L or more, for example, 20 to 200 mg / L, particularly 10 to 30 mg / L, with respect to water added with a heavy metal scavenger.

After adding the heavy metal compound to the reaction equivalent or more and measuring the absorbance or transmittance, the residual collection agent concentration in the heavy metal collection agent-added water is obtained based on the calibration curve (or calibration relationship) obtained in advance. This calibration curve (or calibration relationship) is obtained from the absorbance or transmittance measured by adding a heavy metal compound having a reaction equivalent or higher to an aqueous collecting agent solution having a known concentration.

The measurement of absorbance or transmittance is preferably performed after removing turbidity such as insolubilized material in order to eliminate the influence of insolubilized material. When the heavy metal compound is added to the treated water after the solid-liquid separation treatment, the absorbance can be measured as it is. When a heavy metal compound is added to the heavy metal scavenger-added water before solid-liquid separation, it is desirable to separately remove turbidity by sedimentation separation or filtration before measuring the absorbance.

Based on the thus obtained concentration of the collecting agent in the heavy metal collecting agent-added water, the addition amount of the dithiocarbamic acid heavy metal collecting agent added to the aggregating treatment liquid with the inorganic flocculant is controlled. This control is preferably performed so that the concentration of the collection agent in the heavy metal collection agent-added water falls within the target concentration range.

The lower limit of the target concentration range is, for example, 0 to 10 mg / L, particularly 1 to 5 mg / L, and the upper limit is, for example, about 8 to 50 mg / L, particularly about 10 to 30 mg / L. The target concentration range is preferably 2 to 30 mg / L, more preferably 10 to 20 mg / L, but is not limited thereto.

The measurement wavelength of absorbance or transmittance is 400 to 700 nm, preferably 400 to 660 nm, and particularly preferably 400 to 500 nm. When the wavelength is shorter than this range, it is affected by other organic compounds in the waste water, and the sensitivity is also lowered. If the wavelength is longer than this range, the sensitivity decreases.

An example of the flow of the wastewater treatment method for controlling the amount of the collection agent added to the wastewater based on the concentration of the collection agent in the water such as the solid-liquid separation treated water will be described with reference to FIGS.

In this wastewater treatment system, wastewater containing heavy metal is introduced into the coagulation tank 2 through the raw water pipe 1, added with an inorganic coagulant and coagulated, then introduced into the reaction tank 4, and acid (HCl, etc.) or alkali (NaOH, etc.). The pH adjusting agent is added to adjust the pH, and the dithiocarbamic acid heavy metal scavenger is added from the drug storage tank 3 with the chemical injection pump P and reacted. The liquid in the reaction tank 4 is introduced into the coagulation tank 5 and a polymer coagulant is added for coagulation treatment. The coagulation treatment liquid is solid-liquid separated in the settling basin 6 and the resulting supernatant water is discharged as treated water. To do. The separated sludge is dehydrated with a dehydrator (not shown).

In FIG. 1, a part of the treated water from the sedimentation basin 6 is separated and introduced into the measuring tank 7, a heavy metal compound is added, and the absorbance at 400 to 700 nm is measured with the absorbance meter 8. This absorbance is input to the controller 9, and the required addition amount of the dithiocarbamic acid heavy metal scavenger is calculated. Based on this calculation result, the chemical injection pump P is controlled, and appropriate chemical injection of the dithiocarbamic acid heavy metal scavenger is performed.

In this embodiment, since the inorganic flocculating agent is added to the heavy metal-containing wastewater in the flocculation tank 2 and the flocculation treatment is performed, the dithiocarbamic acid heavy metal scavenger is added in the reaction tank 4, so that the dithiocarbamic acid heavy metal scavenger is The dithiocarbamic acid heavy metal scavenger that has been prevented or suppressed from reacting with the inorganic flocculant and has not reacted with the heavy metal can be measured with the absorptiometer 8 with high accuracy. If the agglomeration tank 2 is installed at the rear stage of the reaction tank 4 and a dithiocarbamic acid heavy metal scavenger is added to the heavy metal-containing wastewater, then an inorganic flocculant is added. The unreacted residual dithiocarbamic acid heavy metal scavenger reacts with the inorganic flocculant in the agglomeration tank on the rear stage side, and the measurement accuracy of the residual scavenger decreases.

In this embodiment, since the inorganic flocculant is added prior to the addition of the dithiocarbamic acid heavy metal scavenger, the suspended matter and part of the soluble COD in the heavy metal-containing wastewater are coagulated. Thereby, the measurement accuracy of the absorbance or transmittance by the absorptiometer 8 is improved.

The absorbance measurement in the measuring tank 7 may be performed continuously or intermittently.

The calculation results of the absorptiometer 8 and the controller 9 are transmitted to the central monitoring device at the remote center via a telephone line via the communication terminal, and a setting change command signal (for example, setting change of measurement interval, Control command value change command signal (such as correction coefficient) is transmitted to the controller via the communication terminal via the telephone line, and the processing status in the remote location is monitored and monitored and controlled remotely by data communication between the local / center. It may be.

In FIG. 1, the absorbance is measured by adding a heavy metal compound to the treated water from the sedimentation basin 6, but as shown in FIG. 2, water is collected from the upper part of the agglomeration tank 5 and introduced into the measurement tank 7. A compound may be added and the absorbance measured. In this case, after filtering the suspension with a filtration membrane, etc., the heavy metal compound is added and stirred, and then measured after standing for a while or sampling water is introduced into the measuring tank 7 and the heavy metal compound is added. After stirring, the mixture is allowed to stand for a while to allow the aggregates to settle, and then the absorbance of the supernatant water is measured. The method and apparatus of FIG. 2 are more susceptible to contamination of the absorbance meter than the method of FIG. 1, but the time lag from the addition of the dithiocarbamic acid-based heavy metal scavenger to the absorbance measurement is small, so accurate control is possible. .

1 and 2, the sedimentation basin 6 is used, but as described above, various solid-liquid separation means can be used.

In the present invention, a transmittance meter can be used in place of the absorbance meter 8.

The method of the present invention and the apparatus can be applied to any heavy metal-containing wastewater as long as it contains a heavy metal capable of reacting with a dithiocarbamic acid heavy metal scavenger.

Hereinafter, the present invention will be described in more detail with reference to experimental examples instead of examples and comparative examples.

<Experimental example 1>
As dithiocarbamate heavy metal scavengers, the absorbance spectra of the four drugs 1 to 4 shown in Table 1 were measured and are shown in FIG. As shown in the figure, each of the collection agents has a strong absorption band at 200 to 350 nm and an absorption peak around 240 nm. Further, the absorbance is extremely small at 400 nm or more.

<Experimental example 2>
As a dithiocarbamic acid heavy metal scavenger, 10 mg / L of FeSO ₄ as Fe ²⁺ was added to 30 mg / L of drug 3 dissolved therein, and the absorbance spectrum was measured. The results are shown in FIG. FIG. 4 also shows the spectrum when FeSO _{4 is} not added.

As shown in FIG. 4, it was confirmed that strong absorption having a peak at 420 nm was generated by adding Fe ²⁺ .

Therefore, the absorbance at 470 nm was measured when the amount of FeSO ₄ added to the 30 mg / L aqueous solution of drug 3 was changed and is shown in FIG. As shown in FIG. 5, the absorbance reached a peak when the Fe ²⁺ addition amount was 10 mg / L or more, and the reaction equivalent of Fe ²⁺ to 30 mg / L of the drug 3 was found to be 10 mg / L.

Thus, the absorbance at 470 nm was measured when the concentration of drug 3 was in the range of 3 to 30 mg / L, and 10 mg / L of FeSO ₄ was added as Fe ²⁺ equal to or higher than the reaction equivalent, and the results are shown in FIG. As shown in FIG. 6, there is a linear relationship between the concentration of the drug 3 and the absorbance. From this, it was confirmed that the concentration of the drug 3 in water can be quantified from the absorbance measured by adding Fe ²⁺ or more to the reaction equivalent.

<Experimental Examples 3 and 4>
In order to confirm the coloring action of heavy metal ions other than Fe ²⁺ , the spectrum when 20 mg / L of CuSO ₄ as Cu ²⁺ was added to 30 mg / L of an aqueous solution of drug 3 was measured and shown in FIG. Example 3). Further, with respect to drug 3 aqueous solution 30 mg / _L, the Fe 2 _(SO _{4) 3} was measured spectrum in the case of 10 mg / L added as ^{Fe 3+,} shown in FIG. 8 (Example 4).

As a result, in the case of Cu ²⁺ and Fe ³⁺ , it was recognized that color development having a peak at about 460 nm (in the case of Cu ²⁺ ) or 360 nm (in the case of Fe ³⁺ ) was caused by reaction with the drug 3. When Al ³⁺ and Ca ²⁺ were added, it was recognized that no color development occurred as shown in FIG.

<Experimental example 5>
Using actual waste water from an automobile factory, a 3 to 36 mg / L aqueous solution of Drug 2 as a dithiocarbamic acid heavy metal scavenger is prepared, and CuSO ₄ or FeSO ₄ is added as Cu ²⁺ or Fe ²⁺ to each 10 mg / L. The absorbance at 425 nm is shown in FIG. As shown in FIG. 9, in the case of the drug 2 as well, it develops color by reacting with Cu ²⁺ and Fe ^2+, and there is a linear correlation between the absorbance and the concentration of the drug 2, and the concentration of the drug 2 is determined from the absorbance. It was recognized that we could do it.

<Experimental example 6>
In Experimental Example 3, the absorbance was measured in the same manner except that the

drug

1 or 4 was used as the dithiocarbamic acid heavy metal scavenger. The results are shown in FIG. As shown in FIG. 10, it is recognized that the

drugs

1 and 4 also react with Cu ²⁺ to develop color.

<Experimental Example 7 (Invention Example)>
In the waste water treatment system shown in FIG. 1, raw water made of simulated waste water simulating heavy metal-containing waste water in an automobile factory was treated. That, Ni, Zn, Cu, Cd , Pb so that the 10 mg-Metal / L _{_{_{respectively, NiSO 4, ZnCl 2, CuSO}}} 4, CdCl 2, FeCl 3 content in the aqueous solution with the addition of PbCl ₂ as the inorganic flocculant 37 % Of commercially available ferric chloride-based flocculant was added at 200 mg / L, and the mixture was stirred and agglomerated. The average residence time in the coagulation tank 2 was 1 min. This agglomeration treatment liquid is introduced into the reaction vessel 4, and a dithiocarbamic acid heavy metal scavenger (Welulin K800 manufactured by Kurita Kogyo Co., Ltd., hereinafter sometimes referred to simply as K800) is added at 500, 900, 1300 or 1700 mg / L. As it was added, NaOH was added to pH = 7.5 and stirred slowly. The average residence time in the reaction vessel 4 was 1 min. The liquid in the reaction tank 4 is introduced into the

coagulation tank

5, and 2 mg / L of an anionic polymer coagulant (Kurita Kogyo Co., Ltd. Cliflock PA331, polyacrylamide type) is added, and the mixture is stirred slowly to coagulate. did. The average residence time in the tank 5 was 1 min.

The coagulation treatment liquid with this polymer coagulant was introduced into the sedimentation basin 6 and subjected to solid-liquid separation treatment.

Treated water from the sedimentation basin 6 was introduced into the measuring

tank

7, and 10 mg / L of ferrous chloride was added as Fe ²⁺ to develop color, and the absorbance at 470 nm was measured. Table 2 shows the measurement results of the absorbance and the Ni ²⁺ and Zn ²⁺ concentrations in the treated water.

As shown in Table 2, it is recognized that the concentration of Ni ²⁺ and Zn ^{2+ in the} treated water is sufficiently reduced by adding the dithiocarbamic acid heavy metal scavenger (K800) so that the absorbance is 0.2 or more. It was. The residual concentration of K800 in the treated water when the absorbance was 0.2 was 5 mg / L.

<Experimental Example 8 (Comparative Example)>
The heavy metal-containing wastewater was treated in the same manner as in Experimental Example 7, except that the dithiocarbamic acid heavy metal scavenger (K800) was first added to the heavy metal-containing wastewater, and then the inorganic flocculant and NaOH were added. Table 3 shows the absorbance and the measurement results of Ni ²⁺ and Zn ²⁺ concentrations in the treated water.

As shown in Table 3, when the dithiocarbamic acid heavy metal scavenger is added before the inorganic flocculant, a part of the dithiocarbamic acid heavy metal scavenger reacts with the inorganic flocculant, resulting in color development in the measuring tank. It became inadequate, and it was recognized that proper medication control was difficult.

<Experimental Example 9 (Invention Example)>
The raw water is an aqueous solution containing 10 mg as Ni / L of NiSO ₄ , 200 mg / L of a commercially available sulfuric acid band type flocculant (Al ₂ O ₃ content 8%) is added as an inorganic flocculant, and addition of a dithiocarbamic acid heavy metal scavenger K800 The experiment was performed under the same conditions as in Experimental Example 7, except that the amount was 0, 100, 300, 500 or 700 mg / L. The results are shown in Table 4.

<Experimental Example 10 (Comparative Example)>
The raw water is an aqueous solution containing 10 mg as Ni / L of NiSO ₄ , 200 mg / L of a commercially available sulfuric acid band type flocculant (Al ₂ O ₃ content 8%) is added as an inorganic flocculant, and addition of a dithiocarbamic acid heavy metal scavenger K800 The experiment was performed under the same conditions as in Experimental Example 8 except that the amount was 0, 100, 300, 500 or 700 mg / L. The results are shown in Table 5.

<Experimental Example 11 (Invention Example)>
Raw water is made into an aqueous solution containing 10 mg as Zn / L of ZnCl ₂ , 200 mg / L of a commercially available sulfuric acid band type flocculant (Al ₂ O ₃ content 8%) is added as an inorganic flocculant, and addition of a dithiocarbamic acid heavy metal scavenger K800 The experiment was performed under the same conditions as in Experimental Example 7, except that the amount was 0, 100, 300, 500 or 700 mg / L. The results are shown in Table 6.

<Experimental Example 12 (Comparative Example)>
Raw water is made into an aqueous solution containing 10 mg as Zn / L of ZnCl ₂ , 200 mg / L of a commercially available sulfuric acid band type flocculant (Al ₂ O ₃ content 8%) is added as an inorganic flocculant, and addition of a dithiocarbamic acid heavy metal scavenger K800 The experiment was performed under the same conditions as in Experimental Example 8 except that the amount was 0, 100, 300, 500 or 700 mg / L. The results are shown in Table 7.

As is clear from Tables 4 to 7, by adding the inorganic flocculant prior to the dithiocarbamic acid heavy metal collector, and adding the dithiocarbamic acid heavy metal collector so that the absorbance is not less than a predetermined value, Ni ²⁺ and Zn ²⁺ are sufficiently removed.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on July 31, 2012 (Japanese Patent Application No. 2012-170051), which is incorporated by reference in its entirety.

2 Coagulation tank 3 Drug storage tank 4 Reaction tank 5 Coagulation tank 6 Sedimentation tank 7 Measurement tank 8 Absorbance meter

Claims

After adding an inorganic flocculant to the heavy metal-containing wastewater and aggregating it, adding a dithiocarbamic acid-based heavy metal scavenger, and then treating the heavy metal-containing wastewater to be solid-liquid separated,
Adding a heavy metal compound to the heavy metal-containing wastewater to which the dithiocarbamic acid heavy metal scavenger is added,
After reacting the heavy metal compound and the dithiocarbamic acid heavy metal scavenger remaining in the heavy metal-containing wastewater to cause color development, the absorbance or transmittance at a wavelength of 400 to 700 nm is measured, and based on the measurement result, A method for treating heavy metal-containing wastewater, characterized in that the addition amount of a dithiocarbamic acid heavy metal scavenger is controlled.
2. The method for treating heavy metal-containing wastewater according to claim 1, wherein the heavy metal compound is a water-soluble iron salt or copper salt.
3. The method for treating heavy metal-containing wastewater according to claim 2, wherein the absorbance or transmittance at a wavelength of 400 to 500 nm is measured.
The dithiocarbamate heavy metal scavenger according to any one of claims 1 to 3, wherein the concentration of the dithiocarbamate heavy metal scavenger in water determined from the absorbance or transmittance is 2 to 30 mg / L. A method for treating heavy metal-containing wastewater, wherein the amount of addition is controlled.
5. The method according to claim 1, wherein after adding an inorganic flocculant to the heavy metal-containing wastewater and aggregating, the dithiocarbamic acid heavy metal scavenger is added without performing solid-liquid separation. A method for treating wastewater containing heavy metals.
6. The heavy metal-containing wastewater to which the dithiocarbamic acid-based heavy metal scavenger to which the heavy metal compound is added is the separated water obtained by the solid-liquid separation according to any one of claims 1 to 5. A method for treating wastewater containing heavy metals.
In any 1 item | term of Claim 1 thru | or 6, after adding an inorganic flocculant to the said heavy metal containing waste water and performing a coagulation process, adding a dithiocarbamic-acid type heavy metal scavenger, and then adding a polymer flocculant and agglomerating A method for treating wastewater containing heavy metal, characterized in that the coagulation treatment liquid is solid-liquid separated.
The heavy metal-containing wastewater to which the dithiocarbamic acid-based heavy metal scavenger to which the heavy metal compound is added is the aggregating treatment liquid according to claim 7, and after adding the heavy metal compound to the aggregating treatment liquid, A method of treating heavy metal-containing wastewater, characterized by measuring the absorbance or transmittance of supernatant water obtained by sedimentation and separation.
After adding an inorganic flocculant to the heavy metal-containing wastewater and aggregating it, adding a dithiocarbamic acid-based heavy metal scavenger, and then treating the heavy metal-containing wastewater to be solid-liquid separated,
Absorbance or transmittance at a wavelength of 400 to 700 nm of the heavy metal-containing wastewater to which the dithiocarbamic acid heavy metal scavenger is added is measured, and the amount of the dithiocarbamic acid heavy metal scavenger is controlled based on the measurement result. A method for treating heavy metal-containing wastewater.
Means for adding an inorganic flocculant to the heavy metal-containing wastewater and aggregating it;
Next, means for adding a dithiocarbamic acid heavy metal scavenger,
Thereafter, a heavy metal-containing wastewater treatment device having solid-liquid separation means for solid-liquid separation,
Means for adding a heavy metal compound to the heavy metal-containing wastewater to which the dithiocarbamic acid heavy metal scavenger is added;
Means for measuring the absorbance or transmittance at a wavelength of 400 to 700 nm after reacting the heavy metal compound and the dithiocarbamic acid heavy metal scavenger in the water to cause color development;
And a control means for controlling the amount of the dithiocarbamic acid heavy metal scavenger added based on the measurement result.
Means for adding an inorganic flocculant to the heavy metal-containing wastewater and aggregating it;
Next, means for adding a dithiocarbamic acid heavy metal scavenger,
Thereafter, a heavy metal-containing wastewater treatment device having solid-liquid separation means for solid-liquid separation,
Means for measuring the absorbance or transmittance at a wavelength of 400 to 700 nm of the heavy metal-containing wastewater to which the dithiocarbamic acid heavy metal scavenger is added;
And a control means for controlling the amount of the dithiocarbamic acid heavy metal scavenger added based on the measurement result.